1. Field of the Invention
This invention is directed to a control surface for controlling an air vehicle such as an aircraft, drone, rocket, missile, or the like. The invention is also directed to air vehicles incorporating the control surface.
2. Description of the Related Art
Aircraft are often required to have the ability to perform at subsonic as well as supersonic speeds. This is especially true of military aircraft. To make high- and low-speed performance possible, aircraft are often equipped with retractable wings with two different sets of control surfaces for high and low speeds. In low-speed operation, the wings are extended to increase lift of the aircraft, and relatively large, low-speed control surfaces are used for steerage. In high-speed operation, the wings are retracted into a delta configuration to reduce drag and lift, and relatively small high-speed control surfaces are used for aircraft control. U.S. Pat. No. 2,665,085 issued Jan. 5, 1954 to F. F. Crocombe et al. is representative of this aircraft type.
Although these aircraft have proven functional at subsonic and supersonic speeds, it is desirable to simplify the control surfaces and related equipment, and to eliminate the need for wing retraction and extension mechanisms, which greatly increase the complexity, expense and weight of the aircraft.
This invention overcomes the above-noted disadvantages. The invented apparatus includes at least one control surface having upper and lower major surfaces, that is positioned at the outboardmost tip of an air vehicle""s flight structure. The flight structure can be any structure that extends outwardly from the air vehicle""s central axis into the air stream, that provides airfoil lift and/or control in flight. For example, the flight structure can be a wing, a vertical or horizontal tail, or other stabilizer of an aircraft (including drones), a rocket or missile. The control surface is approximately L-shaped, and has upper and lower major surfaces extending along a single plane including perpendicular length-wise and span-wise dimensions which are the largest dimensions of the control surface. The control surface also has a relatively small dimension along the height-wise direction between the upper and lower surfaces of the control surface. The control surfaces defines the outboardmost tip relative to the air vehicle""s central axis, or equivalently, the outboardmost leading and trailing edges of the flight structure to which it is mounted. Hence, the control surface is referred to as a xe2x80x98tiperonxe2x80x99. The control surface is preferably mounted to a fixed portion of the flight structure for rotation about a control axis. For example, the control surface can be mounted to the air vehicle""s flight structure with a set-back, serial, or piano hinge, or other suitable device. If implemented in a wing, the control surface is configured so that the subsonic and supersonic centers of pressure, and preferably also the subsonic and supersonic centroids of pressure area, are situated aft of the control axis on the underside thereof, and forward of the centroid of the surface area of the control surface. This relative positioning of the centers of pressure and centroids of pressure area relative to the control axis and centroid of surface area improves the stability of the air vehicle and facilitates its control. Such positioning of the centers of pressure and centroids of pressure area relative to the control axis and centroid of surface area is accomplished by proportioning the surface areas of control surface sections forward and aft of the control axis so that the section situated forward of the control axis has less surface area than does the section situated aft of the control axis, and by cambering of the control surface. Also, the control surface is preferably configured so that the mass forward and aft of the control axis is balanced, or substantially so, a feature which is important and possibly imperative for controlling the air vehicle at high speeds. Further, the control surface section situated forward of the control axis is tapered in cross-section along a plane of the length-wise and span-wise dimensions of the control surface, and has a tapered or wedge form in cross-section along a plane including span-wise and height-wise dimensions. The tapering of this section of the control surface reduces the dependence of the moment exerted by air flow upon the surface""s angle-of-attack, and consequently, the surface can be more easily controlled. The control surface section that is situated aft of the control axis can be approximately rectangular or trapezoidal in cross-section along a plane including the length-wise and span-wise dimensions of the control surface. The aft section of the control surface preferably extends along the flight structure""s span direction beyond the side edge of the control surface""s tapered section forward of the control axis. The control surface section aft of the control axis is also tapered or wedge-shaped in cross-section along the plane parallel to the length-wise and height-wise dimensions. The control surface can be cambered to form an integral part of the flight structure""s airfoil if the control surface is positioned about its control axis to be approximately flush or level with the remainder of the flight structure. In the case in which the flight structure is a wing, these features help to increase the air vehicle""s lift, a benefit of considerable importance particularly in aircraft operation at low airspeeds. Such features also allow the aircraft to function effectively at low and high Mach-numbers at which the control surface""s integration with the remainder of the flight structure can be important or critical, and at which relatively small deflections of the control surface can be used to control flight to the limits of the air vehicle""s performance capability.
In one implementation, the control surface""s leading edge defines an outer sweep of a double-delta wing platform. However, the control surface can be used in various ways in many kinds of air vehicles, including in the outboardmost or aftmost portion of a delta-wing aircraft""s leading edge, the outboardmost tips of straight- or swept-wing aircraft, vertical or horizontal aircraft tails, or missile or rocket stabilizers or wings (as in the cruise missile), for example.
The invented aircraft includes a body with an integrated wing-body structure. Tiperon control surfaces as previously described are movably mounted to the port and starboard sides of the wing-body structure of the aircraft. Actuators are coupled to and control the positions of respective control surfaces. These actuators can be servomotors or hydraulically-actuated devices, for example. The actuators are in turn coupled to and controlled by the aircraft""s flight control system (FCS). The FCS controls the actuators, and hence also the surfaces, based upon a control signal, and optionally also upon feedback signals from the actuators. The control signal can be generated by pilot or autopilot inputs generated onboard or remotely, an onboard processor or other device, or by the FCS itself, for example, to perform a desired or preprogrammed flight action or mission. The FCS can thus be used to control the angular position relative to the aircraft wing, of the two control surfaces about respective control axes, and thus to control the roll and pitch of the aircraft, and optionally also the aircraft""s yaw attitude if no rudders are used. With the present invention, the aircraft""s control can be greatly simplified by the use of only two control surfaces, and optionally one or more rudders. If desirable in a particular aircraft, the FCS can be omitted and mechanical linkages and levers coupled between the pilot""s control instruments directly to the control surfaces, can be used to deflect the tiperon control surfaces for aircraft control. Also, for most wing designs, the control surface requires no trim tabs, a feature which further reduces aircraft control complication. In addition, if other control surfaces are present to control the aircraft""s pitch attitude, the FCS and/or pilot can control the invented surfaces to deflect their leading edges upward with respect to fixed portions of the wing to act as landing flaps, or can deflect their leading edges downward with respect to fixed portions of the wing to act as spoilers to reduce the aircraft""s speed.
These together with other features and advantages, which will become subsequently apparent, reside in the details of construction and operation as more fully hereinafter described and claimed, reference being made to the accompanying drawings, forming a part hereof, wherein like numerals refer to like parts throughout the several views.